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The atria and ventricles work together, alternately contracting and relaxing to
pump blood through your heart. The electrical system of your heart is the power
source that makes this possible. Your heartbeat is triggered by electrical impulses
that travel down a special pathway through your heart:
1. SA node (sinoatrial node) – known as the heart’s natural pacemaker
The impulse starts in a small bundle of specialized cells located in the right
atrium, called the SA node. The electrical activity spreads through the walls of
the atria and causes them to contract. This forces blood into the ventricles.
The SA node sets the rate and rhythm of your heartbeat. Normal heart rhythm is often
called normal sinus rhythm because the SA (sinus) node fires regularly.
2. AV node (Atrioventricular node)
The AV node is a cluster of cells in the center of the heart between the atria and
ventricles, and acts like a gate that slows the electrical signal before it enters
the ventricles. This delay gives the atria time to contract before the ventricles
do.
3. His-Purkinje Network
This pathway of fibers sends the impulse to the muscular walls of the ventricles
and causes them to contract. This forces blood out of the heart to the lungs and
body.
4. The SA node fires another impulse and the cycle begins again.
At rest, a normal heart beats around 50 to 99 times a minute. Exercise, emotions,
fever and some medications can cause your heart to beat faster, sometimes to well
over 100 beats per minute.
How fast does the normal heart beat?
How fast the heart beats depends on the body's need for oxygen-rich blood. At rest,
the SA node causes your heart to beat about 50 to 100 times each minute. During
activity or excitement, your body needs more oxygen-rich blood; the heart rate rises
to well over 100 beats per minute.
Medications and some medical conditions may affect how fast your heart-rate is at
rest and with exercise.
How do you know how fast your heart is beating?
You can tell how fast your heart is beating (your heart rate) by feeling your pulse.
Your heart-rate is the amount of times your heart beats in one minute.
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The heart works 24 hours a day, pumping oxygen- and nutrient-rich blood to the body.
Blood is supplied to the heart through its coronary arteries. In coronary heart
disease (CHD), plaques or fatty substances build up inside the walls of the arteries.
The plaques also attract blood components, which stick to the artery wall lining.
Called atherosclerosis, the process develops gradually, over many years. It often
begins early in life, even in childhood. The fatty buildup or plaque can break open
and lead to the formation of a blood clot that seals the break. The clot reduces
blood flow. The cycle of fatty buildup, plaque rupture, and blood clot formation
causes the coronary arteries to narrow, reducing blood flow.
When too little blood reaches the heart, the condition is called ischemia. Chest
pain, or angina, may occur. The pain can vary in occurrence and be mild and intermittent,
or more pronounced and steady. It can be severe enough to make normal everyday activities
difficult. The same inadequate blood supply also may cause no symptoms, a condition
called silent ischemia.
If a blood clot suddenly cuts off most or all blood supply to the heart, a heart
attack results. Cells in the heart muscle that do not receive enough oxygen-carrying
blood begin to die. The more time that passes without treatment to restore blood
flow, the greater the damage to the heart.
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What Is Angina?
Angina (an-JI-nuh or AN-juh-nuh) is chest pain or discomfort that occurs when your
heart muscle does not get enough blood. Angina may feel like pressure or a squeezing
pain in your chest. The pain may also occur in your shoulders, arms, neck, jaw,
or back. It may also feel like indigestion.
Angina is a symptom of coronary artery disease (CAD), the most common type
of heart disease. CAD occurs when plaque builds up in the coronary arteries. This
buildup of plaque is called atherosclerosis. As plaque builds up, the coronary arteries
become narrow and stiff. Blood flow to the heart is reduced. This decreases the
oxygen supply to the heart muscle.
Types of Angina
The three types of angina are stable, unstable, and variant (Prinzmetal's). It is
very important to know the differences among the types.
Stable angina: Stable angina is the most common type. It occurs when the
heart is working harder than usual. There is a regular pattern to stable angina.
After several episodes, you learn to recognize the pattern and can predict when
it will occur. The pain usually goes away in a few minutes after you rest or take
your angina medicine. Stable angina is not a heart attack but makes it more likely
that you will have a heart attack in the future.
Unstable angina: Unstable angina is a very dangerous condition that requires
emergency treatment. It is a sign that a heart attack could occur soon. Unlike stable
angina, it does not follow a pattern. It can occur without physical exertion and
is not relieved by rest or medicine.
Variant angina: Variant angina is rare. It usually occurs at rest. The pain
can be severe and usually occurs between midnight and early morning. It is relieved
by medicine.
Not all chest pain or discomfort is angina. Chest pain or discomfort can be caused
by a heart attack, lung problems (such as an infection or a blood clot), heartburn,
or a panic attack. However, all chest pain should be checked by a doctor.
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What Is Coronary Artery Disease?
Coronary artery disease (CAD) occurs when the arteries that supply blood to the
heart muscle (the coronary arteries) become hardened and narrowed. The arteries
harden and narrow due to buildup of a material called plaque (plak) on their inner
walls. The buildup of plaque is known as atherosclerosis (ATH-er-o-skler-O-sis).
As the plaque increases in size, the insides of the coronary arteries get narrower
and less blood can flow through them. Eventually, blood flow to the heart muscle
is reduced, and, because blood carries much-needed oxygen, the heart muscle is not
able to receive the amount of oxygen it needs. Reduced or cutoff blood flow and
oxygen supply to the heart muscle can result in:
Angina (AN-ji-na or an-JI-na). Angina is chest pain
or discomfort that occurs when the heart does not get enough blood.
Heart attack. A heart attack happens when a blood clot develops at the site
of plaque in a coronary artery and suddenly cuts off most or all blood supply to
that part of the heart muscle. Cells in the heart muscle begin to die if they do
not receive enough oxygen-rich blood. This can cause permanent damage to the heart
muscle.
Over time, CAD can weaken the heart muscle and contribute to:
Heart failure. In heart failure, the heart can’t pump
blood effectively to the rest of the body. Heart failure does not mean that the
heart has stopped or is about to stop. Instead, it means that the heart is failing
to pump blood the way that it should.
Arrhythmias (a-RITH-me-as). Arrhythmias are changes in the normal beating
rhythm of the heart. Some can be quite serious.
CAD is the most common type of heart disease. It is the leading cause of death in
the United States in both men and women.
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What Is an Arrhythmia?
An arrhythmia (ah-RITH-me-ah) is a problem with the speed or rhythm of the heartbeat.
During an arrhythmia, the heart can beat too fast, too slow, or with an irregular
rhythm. A heartbeat that is too fast is called tachycardia. A heartbeat that is
too slow is called bradycardia.
Most arrhythmias are harmless, but some can be serious or even life threatening.
When the heart rate is too slow, too fast, or irregular, the heart may not be able
to pump enough blood to the body. Lack of blood flow can damage the brain, heart,
and other organs.
The heart has an internal electrical system that controls the speed and rhythm of
the heartbeat. With each heartbeat, an electrical signal spreads from the top of
the heart to the bottom. As it travels, the electrical signal causes the heart to
contract and pump blood. The process repeats with each new heartbeat. Each electrical
signal begins in a group of cells called the sinus node, or sinoatrial (SA) node.
The SA node is located in the right atrium (AY-tree-um), which is the upper right
chamber of the heart. In a healthy adult heart at rest, the SA node fires off an
electrical signal to begin a new heartbeat 60 to 100 times a minute.
From the SA node, the electrical signal travels through special pathways to the
right and left atria. This causes the atria to contract and pump blood into the
heart’s two lower chambers, the ventricles (VEN-trih-kuls). The electrical signal
then moves down to a group of cells called the atrioventricular (AV) node, located
between the atria and the ventricles. Here, the signal slows down just a little,
allowing the ventricles time to finish filling with blood. The electrical signal
then leaves the AV node and travels along a pathway called the bundle of His. This
pathway divides into a right bundle branch and a left bundle branch. The signal
goes down these branches to the ventricles, causing them to contract and pump blood
out to the lungs and the rest of the body. The ventricles then relax, and the heartbeat
process starts all over again in the SA node.
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What Is Heart Failure?
Heart failure is a condition in which the heart can’t pump enough blood throughout
the body. Heart failure does not mean that your heart has stopped or is about to
stop working. It means that your heart is not able to pump blood the way that it
should. The heart can’t fill with enough blood or pump with enough force, or both.
Heart failure develops over time as the pumping action of the heart grows weaker.
It can affect the left side, the right side, or both sides of the heart. Most cases
involve the left side where the heart can’t pump enough oxygen-rich blood to the
rest of the body. With right-sided failure, the heart can’t effectively pump blood
to the lungs where the blood picks up oxygen.
The weakening of the heart’s pumping ability causes:
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Blood and fluid to "back up" into the lungs
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The buildup of fluid in the feet, ankles, and legs
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Tiredness and shortness of breath
Heart failure is a serious condition. About 5 million people in the United States
have heart failure, and the number is growing. Each year, another 550,000 people
are diagnosed for the first time. It contributes to or causes about 300,000 deaths
each year.
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What Is an Electrocardiogram?
An electrocardiogram, also called an EKG or ECG, is a simple test that detects and
records the electrical activity of the heart. It is used to detect and locate the
source of heart problems.
Electrical signals in the heart trigger heartbeats. These signals start at the top
of the heart in an area called the right atrium. The electrical signals travel from
the top of the heart to the bottom. They cause the heart muscle to contract as they
travel through the heart. As the heart contracts, it pumps blood out to the rest
of the body.
An EKG shows how fast the heart is beating. It shows the heart’s rhythm (steady
or irregular) and where in the body the heartbeat is being recorded. It also records
the strength and timing of the electrical signals as they pass through each part
of the heart.
An EKG is sometimes called a 12-lead EKG (or 12-lead ECG) because the electrical
activity of the heart is most often recorded from 12 different places on the body
at the same time.
Many heart problems change the electrical signature of the heart in distinct ways.
EKG recordings of this electrical activity can help reveal a number of heart problems,
including:
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Heart attack
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Lack of blood flow to the heart muscle
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A heart that is beating irregularly, or too fast or too slow
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A heart that does not pump forcefully enough
EKG recordings can help doctors diagnose a heart attack that is happening now or
has happened in the past. This is especially true if doctors can compare a current
EKG recording to an older one. EKG recordings can also reveal:
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Heart muscle that is too thick or parts of the heart that are too big
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Birth defects in the heart
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Disease in the heart valves between the different heart chambers
An EKG also reveals whether the heartbeat starts at the top right part of the heart
like it should. It shows how long it takes for the electrical signals to travel
through the heart.
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Echocardiogram is a test that uses sound waves to create a moving picture of the
heart. The picture is much more detailed than x-ray image and involves no radiation
exposure.
A trained sonographer performs the test, then your physician interprets the results.
An instrument that transmits high-frequency sound waves called a transducer is placed
on your chest near the breast bone and directed toward the heart. The transducer
picks up the echoes of the sound waves and transmits them as electrical impulses.
The echocardiography machine converts these impulses into moving pictures of the
heart.
Echocardiogram works well for most patients and allows doctors to see the heart
beating and to visualize many of the structures of the heart. Occasionally, because
your lungs, ribs, or body tissue may prevent the sound waves and echoes from providing
a clear picture of heart function, the sonographer may administer a small amount
of a dye through an IV to better see the inside of the heart. Very rarely, more
invasive testing using special echocardiography probes may be necessary.
If the echocardiogram is unclear due to a barrel chest, chronic obstructive Lung
disease, or obesity, your health care provider may choose to perform a transesophageal
echocardiogram, or TEE. With TEE, the back of your throat is anesthetized and a
scope is inserted down your throat. On the end of the scope is an ultrasonic device
that a cardiologist will guide down to the lower part of the esophagus,
where it is used to obtain a more clear two-dimensional echocardiogram of your heart.
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An exercise stress test is a screening tool to test the effect of exercise on your
heart. The test gives a general sense of how healthy your heart is.
You will walk or pedal on an exercise machine while the electrical activity of your
heart is measured with an electrocardiogram (ECG), and blood pressure readings are
taken. This will measure your heart's reaction to your body's increased need for
oxygen.
The test continues until you reach a target heart rate, unless complications such
as chest pain or an exaggerated rise in blood pressure develop. You will continue
to be monitored for 10 - 15 minutes after exercising, or until your heart rate returns
to baseline.
A stress test is performed to determine causes of chest pain, the exercise capacity
of the heart, appropriate exercise levels in those beginning an exercise program,
and to identify rhythm disturbances during exercise. There may be additional reasons
that your health care provider requests this test.
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Thallium and sestamibi stress tests are nuclear imaging methods that provide a view
of the blood flow into the heart muscle. The thallium and sestamibi tests are also
called “MIBI stress test” and “myocardial perfusion scintigraphy”, and are used
to evaluate how well your heart is perfused (supplied with blood) at rest as compared
with activity.
During these tests, heart images can be obtained because the patient receives an
injection of a substance that is labeled with a radioactive marker or radiotracer
to make it visible in the bloodstream. These substances are also called radiopharmaceuticals,
and include thallium-201 and technetium-99m MIBI or sestamibi.
In comparison to the standard treadmill stress test, thallium and sestamibi stress
tests are more accurate and provide additional information.
At our St. Paul Office you will be instructed to exercise as hard as you can on
a treadmill or bicycle. If your doctor considers that exercise is not safe for you,
or that you may be unable to exercise enough because of orthopedic problems, then
you will be given an intravenous medication that will challenge your heart as if
you were exercising.
When you reach your maximum level of exercise, a nurse will inject in your vein
a small amount of a radioactive substance (radiotracer), either thallium or sestamibi.
The radiotracer will travel in the bloodstream and, through the coronary arteries,
will enter into the heart muscle as you complete your exercise session.
After you finish exercising, you will lie down on a special table under a bulky
camera called a gamma camera. The gamma camera can scan your heart and detect the
radiotracer in it. The distribution of the radiotracer in your heart will be processed
by a computer to create pictures of your heart. The first pictures are made shortly
after the exercise test, to show the circulation of blood to your heart during exercise.
This is the part considered "a stress test" and is the most challenging for your
heart.
Then you will need to lie quietly for 2-3 hours, and at that point the scanner will
make another series of pictures of your heart. These images will show the circulation
of blood through your heart muscle at rest.
If your doctor has indicated that your test should be performed without exertion,
then at the beginning of the test you will not exercise, but instead will receive
an intravenous medication, a vasodilator (usually dipyridamole or adenosine). This
medication will selectively dilate (widen) the coronary arteries as long as they
are normal; arteries with blockages will receive less blood flow and will be less
dilated, allowing less blood flow into the heart muscle. After this initial medication,
you will receive the injection with the radiotracer. The test done using a vasodilator
can potentially show a defect in the same way as the test with exercise does.
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An invasive imaging procedure that involves inserting a catheter into a blood vessel
in the arm or leg, and guiding it to your heart with the aid of a special x-ray
machine. Contrast dye is injected through the catheter so that x-ray movies of your
valves, coronary arteries and heart chambers are taken.
Your doctor uses cardiac cardiac cath to:
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evaluate or confirm the presence of heart disease (such as coronary artery disease,
valve disease or disease of the aorta)
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evaluate heart muscle function
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determine the need for further treatment (angioplasty or bypass surgery)
The x-ray camera will be used to take photographs of the arteries and heart chambers.
You will be asked to hold your breath while the x-rays are taken. When all the photos
have been taken, the catheter will be removed and the lights will be turned on.
You may have an interventional procedure combined with your cardiac catheterization.
After the procedure:
The catheters and sheath are removed.
If the catheter was inserted in the arm: The incision will be bandaged. You
will need to keep your arm straight for at least an hour. You will be able to walk
around. You will be observed for a few hours to monitor any symptoms or side effects
of the procedure. You will be given instructions regarding how to care for your
arm when you return home. Tell your nurse if you think you are bleeding (wet, warm
sensation) or feel any numbness or tingling in your fingers.
If the catheter was inserted at the groin: The incision will be closed with
applied pressure, suture device or a "plug." A "plug" is a material which works
with your body's natural healing processes to form a clot in the artery. You will
need to lie flat and keep the leg straight for two to six hours to prevent bleeding
(less time if a plug was used). Your head cannot be raised more than 30 degrees
(2 pillows high). Do not try to sit or stand.
A sterile dressing will be placed on the groin area to protect it from infection.
The nurse will check your bandage regularly, but call your nurse if you think you
are bleeding (have a wet, warm sensation) or if your toes begin to tingle or feel
numb. You will need to drink plenty of liquids to clear the contrast material from
your body. You may feel the need to urinate more frequently. This is normal. If
you are on bedrest, you will need to use a bedpan or urinal.
Your doctor will tell you if you are able to return home or will need to stay overnight.
In either case, you will be monitored for several hours after the procedure.
Treatment, including medications, diet and future procedures, will be discussed
with you prior to going home. Care of the wound site, activity and follow-up care
will also be discussed.
The cardiac cath procedure only takes about 30 minutes, but plan to spend about
5 to 9 hours from the preparation through the recovery time.
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What are interventional procedures?
An interventional procedure is a non-surgical treatment used to open narrowed coronary
arteries to improve blood flow to the heart. An interventional procedure can be
performed during a diagnostic cardiac catheterization when a blockage is identified,
or it may be scheduled after a catheterization has confirmed the presence of coronary
artery disease. An interventional procedure starts out the same way as a cardiac
catheterization. Once the catheter is in place, one of these interventional procedures
is performed to open the artery: balloon angioplasty, stent placement, rotoblation
or cutting balloon.
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Balloon angioplasty: (Percutaneous Transluminal Coronary Angioplasty or PTCA) A
procedure in which a small balloon at the tip of the catheter is inserted near the
blocked or narrowed area of the coronary artery. The technical name for balloon
angioplasty is percutaneous transluminal coronary angioplasty (PTCA) or percutaneous
coronary intervention (PCI). When the balloon is inflated, the fatty plaque or blockage
is compressed against the artery walls and the diameter of the blood vessel is widened
(dilated) to increase blood flow to the heart.
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Balloon Angioplasty |
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balloon is inflated to compress fatty matter |
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Balloon Angioplasty with Stenting |
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stent stays in place after catheter is removed |
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Balloon Angioplasty with stenting:
In most cases, balloon angioplasty is performed in combination with the stenting
procedure. A stent is a small, metal mesh tube that acts as a scaffold to provide
support inside the coronary artery. A balloon catheter, placed over a guide wire,
is used to insert the stent into the narrowed artery. Once in place, the balloon
is inflated and the stent expands to the size of the artery and holds it open. The
balloon is deflated and removed, and the stent stays in place permanently. During
a period of several weeks, the artery heals around the stent.
Angioplasty with stenting is most commonly recommended for patients who have a blockage
in one or two coronary arteries. If there are blockages in more than two coronary
arteries, coronary artery bypass graft surgery may be recommended.
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Rotablation (Percutaneous Transluminal Rotational Atherectomy or PTRA):
A special catheter, with an acorn-shaped, diamond-coated tip, is guided to the point
of narrowing in the coronary artery. The tip spins around at a high speed and grinds
away the plaque on the arterial walls. This process is repeated as needed to treat
the blockage and improve blood flow. The microscopic particles are washed safely
away in your blood stream and filtered out by your liver and spleen.
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Rotablation |
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tip spins at high speed to grind plaque away |
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Cutting Balloon |
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used with permission from Boston Scientific Corp. |
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Cutting Balloon
The cutting balloon catheter has a balloon tip with small blades. When the balloon
is inflated, the blades are activated. The small blades score the plaque, then,
the balloon compresses the fatty matter into the arterial wall. This type of balloon
may be used to treat the build up of plaque within a previously placed stent (restenosis).
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Are these procedures considered to be surgical procedures?
No. Cardiac catheterization and interventional procedures are not considered to
be surgical procedures because there is no large incision used to open the chest,
and the recovery time from catheterization is much shorter than that of surgery.
In some cases, surgery may be recommended afterward, depending on the results of
the procedure.
Will I be awake during the procedure?
Yes. You will be given a mild sedative to relax you, but you will be awake and conscious
during the entire procedure. The doctor will use a local anesthetic to numb the
catheter insertion site.
Where are the procedures performed?
The catheterization and interventional procedures are performed in the Cardiac Catheterization
Laboratory at the Hospital.
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A pacemaker is a small electrical device that is placed inside your body to help
your heart keep up with a steady beat. A pacemaker may be needed when you heart’s
natural pacemaker is not working properly.
Having a pacemaker means you will have to take care of certain precautions. But
with proper care, you can live a healthy, active life. You may find that you are
able to return to activities you have not been able to do for a while. Knowing more
about your heart will help you understand how a pacemaker can help you.
Putting a pacemaker in your body is called implantation. You will be awake for the
procedure. The skin where the incision will be made is numbed. The incision is made
in the upper chest just over the vein. A pocket is formed under the muscle where
the pacemaker will be placed.
The vein just under the incision is opened. The lead is placed inside the vein and
guided into your heart. If there are two leads, the second lead is guided through
the vein into the heart. The generator is attached to the lead. The pacemaker is
then put inside the pocket under your skin. After the procedure, your heart will
be monitored and your incision will be checked for signs of bleeding. You may be
asked not to use the arm on the side of your incision for a short time.
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You will be told how to care for your incision
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Your pacemaker will need to be checked periodically
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Pacemaker batteries will be checked often and replaced when they begin to wear out
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